Electronic synergy to boost the performance of NiCoP-NWs@FeCoP-NSs anodes for flexible lithium-ion batteries

Research and development of flexible lithium-ion batteries (LIBs) with high energy density and long cycle life for portable and wearable electronic devices has been a cutting-edge effort in recent years. In this paper, a novel flexible self-standing anode for LIBs is fabricated successfully, in which NiCoP nanowires (NWs) coated with FeCoP nanosheets (NSs) to form core-shell heterostructure arrays are grown on carbon cloth (CC) (designated as NiCoP-NWs@FeCoP-NSs/CC). The obtained NiCoP-NWs@FeCoP-NSs/CC anode integrates the merits of the one-dimensional (1D) NiCoP-NW core and two-dimensional (2D) FeCoP-NS shell and the CC to show a high lithium-ion storage capacity with long-term cycling stability (1172.6 mA h g(-1) at 1 A g(-1) up to 300 cycles with a capacity retention of 92.6%). The kinetics studies demonstrate that the pseudocapacitive behavior dominates the fast lithium storage of this anode material. For fundamental mechanistic understanding, density functional theory (DFT) analysis is carried out, and manifests that electronic synergy can boost the superior performance of the NiCoP-NWs@FeCoP-NSs/CC anode. The assembled LiFePO4//NiCoP-NWs@FeCoP-NSs/CC full battery gives a discharge capacity of 469.9 mA h g(-1) at 0.5 A g(-1) after 500 cycles, and even at 2 A g(-1), it still can retain 581.5 mA h g(-1). Besides, the soft pack full battery can keep the LED lit continuously when it is folded at different angles and maintain brightness for a period of time, highlighting the large application potential of this flexible LIB for wearable electronic devices. This work provides an idea for the design and construction of advanced metal phosphide flexible electrodes for LIBs.

Two-Dimensional Transition Metal Carbides and Nitrides (MXenes): Synthesis, Properties, and Electrochemical Energy Storage Applications

Sina Abdolhosseinzadeh, Jakob Heier, Chi Zhang

A family of 2D transition metal carbides and nitrides known as MXenes has received increasing attention since the discovery of Ti3C2 in 2011. To date, about 30 different MXenes with well-defined structures and properties have been synthesized, and many more are theoretically predicted to exist. Due to the numerous assets including excellent mechanical properties, metallic conductivity, unique in-plane anisotropic structure, tunable band gap, and so on, MXenes rapidly positioned themselves at the forefront of the 2D materials world and have found numerous promising applications. Particular interest is devoted to applications in electrochemical energy storage, whereby 2D MXenes work either as electrodes, additives, separators, or hosts. This review summarizes recent advances in the synthesis, fundamental properties and composites of MXene and highlights the state-of-the-art electrochemical performance of MXene-based electrodes/devices. The progresses in the field of supercapacitors and Li-ion batteries, Li-S batteries, Na- and other alkali metal ion batteries are reviewed, and current challenges and new opportunities for MXenes in this surging energy storage field are presented. In the focus of interest is the possibility to boost device-level performance, particularly that of rechargeable batteries, which are of utmost importance in future energy technologies. Very recently, the 2019 Nobel Prize in Chemistry was awarded to the inventors of the Li-ion battery. For sure, this will provide an additional stimulation to study fundamental aspects of electrochemical energy storage.

2020

SnSb binary alloy induced heterogeneous nucleation within the confined nanospace: Toward dendrite-free, flexible and energy/power dense sodium metal batteries

Dou Du, Yujie Liu, Min Zhang

Rechargeable sodium (Na) metal batteries (SMBs) provide an alternative energy-dense, low-cost energy storage system beyond prevailing Li-ion technologies. However, their practical deployment requires the performance evaluation of Na anodes on the device level and mitigation of safety hazards, i.e., mechanical stress, electrode pulverization and dynamic interfacial properties. Here, we propose a lightweight N-doped carbon nanofiber substrate with SnSb nanocrystallites monodispersed within the mesopores (SnSb@NCNF). The alloying-induced Na15Sn4 and Na3Sb intermediates act as the heterogeneous sodiophilic "magnets" to homogenize Na ion flux and confine Na deposits within the nanospace. Additionally, the nucleation theory of metal solidification bridges the density functional theory calculations, elucidating the oriented Na propagation that maximizes the anode utilization. With the proper Na plating regulation, the SnSb@NCNF substrate (pre-stored 1 x excess Na) integrates with the NaVPO4F cathode in 5 mA h single-layer pouch cell, the prototype of which exhibits the cycling endurance (96.3% capacity retention for 500 cycles) and high specific energy/power densities even upon the repetitive mechanical flexing scenarios. The nanoconfinement of the heterogeneous nucleation process affords a feasible approach to mitigate the dendrite formation upon the geometry deformation or high areal-capacity loading, which enlightens the further exploration of the energy-dense, mechanical flexible battery system.

ELSEVIER2021